Automatic engine cranking system

ABSTRACT

A system for energizing the vehicle engine starter motor when the vehicle engine stalls while the vehicle is at a speed greater than a predetermined minimum so as to maintain the operation of the vehicle driven accessories while the vehicle speed is greater than the predetermined minimum and to maintain the requirement of manual start while the vehicle is at rest.

United States Patent 11 1 Pasek et al.

[ 1 I I I AUTOMATIC ENGINE CRANKING SYSTEM Inventors: James E. Pasek; Frederick L. J. I Rehfeld, both of Saginaw; William B. Thompson, Frankenmuth, all of [45] Feb. 6, 1973 References Cited Mich Primary Examiner-Laurence M. Goodridge Assignee: General Motors Corporation, y Meland Detroit, Mich. I [57] ABSTRACT Filed: Sept. 1, 1971 A system for energizing the vehicle engine starter PP 176,813 motor when the vehicle engine stalls while the vehicle is at a speed greater than a predetermined minimum U S 180/103 [80/105 E 123/179 K so as to maintain the operation of the vehicle driven i 27/00 accessories while the vehicle speed is greater than the i predetermined minimum and to maintain the q Field 9 Search "123/179 8 0/ ;O 5 ment of manual start while the vehicle is at rest.

1 Claim, 2 Drawing Figures WHEEL TACHOMETER BISTABLE SPEED SENSOR CIRCUIT SWITCH 17 XZ L VEHICLE ENGINE GATE STARTER MOTOR IGNITION TACHOMETER BISTABLE I SYSTEM CIRCUIT SWITCH WHEEL TACHOMETER BISTABLE SPEED ENS R clRculT SWITCH I 32 f /H /2 41 VEHICLE ENGINE GATE STARTER MOTOR IGNITION TACHOMETER BISTABLE I n SYSTEM CIRCUIT SWITCH TO SPARK PLUGS INVENTORS AUTOMATIC ENGINE CRANKING SYSTEM This invention relates to an automatic cranking system for a vehicle engine and, more specifically, this invention relates to an automatic cranking system for maintaining the operation of vehicle engine powered accessories in the event of an engine stall while the vehicle is in motion.

Transmission fluid pumps for automatic transmis sions of the type whichare currently installed on automotive vehicles are driven by the vehicle engine. Consequently, when the vehicle engine stalls, the loss of transmission fluid pressure disables the transmission and prevents the engine from being driven by the drive wheels through the drive train while the vehicle is in motion even though the transmission selector lever is in a drive position. Therefore, in the event of an engine stall, the vehicle engine speed drops to zero which results in the loss of operation of the engine driven accessories, such as, for example, .power steering assist. It is, therefore, one object of this invention to provide an automatic cranking system for energizing the vehicle starter motor upon the occurrence of an engine stall while the vehicle is inmotion so as to maintain opera tion of the engine driven accessories.

Automotive vehicles are also currently manufactured with a neutral and park safety switch which prevents the energization of the starter motor solenoid when the vehicle transmission selector lever is in drive or reverse positions. It is an object of this invention to provide an automatic cranking system for energizing the vehicle starter motor at all positions of the transmission selector lever when the vehicle engine stalls while the vehicle is moving at a predetermined minimum speed, which does not replace the function of 5 manual start when the vehicle is at rest including the requirement that the vehicle selector lever be placed in neutral or park position prior to the manual start.

These and other objects of this invention are accomplished by monitoring the vehicle speed and the engine speed and energizing the vehicle starter solenoid when the vehicle speed is above a predetermined minimum speed and the engine speed is at a speed which represents a stalled condition. The starter motor cranks the vehicle engine to maintain the operation of the engine driven accessories until the vehicle engine restarts or until the vehicle speed decreases below the predetermined minimum.

The invention may be best understood by reference to the following description ofa preferred embodiment and the figures in which:

FIG. 1 is a block diagram of the preferred embodi-' ment of this invention; and

FIG. 2 is an electrical schematic of one means for accomplishing the functions of the block diagram of FIG. 1

Referring to FIG. 1, a wheel speed sensor 10 is driven by a member of the vehicle drive train and supplies to a tachometer circuit 12 a signal having a frequency directly related to the speed of the vehicle. The output of the tachometer circuit 12 is a signal having a magnitude directly proportional to the speed of the vehicle. A bistable switch 14 is responsive to the output of the tachometer circuit 12 for switching from a first state to a second state when the output of the tachometer circuit 12 is at or above a value which represents a predetermined minimum speed of the vehicle and, conversely, switches from the second state to the first state when the output of the tachometer 12 is below a value which represents a speed less than the predetermined speed.

A tachometer circuit 16 is connected to the vehicle ignition system 18 and receives therefrom a waveform having a frequency directly proportional to the speed of the vehicle engine. The tachometer circuit 16 generates a signal in response to the frequency of the waveform at the input thereof having a magnitude directly proportional to the speed of the vehicle engine. A bistable switch 20 is responsive to the output of the tachometer circuit 16 for switching from a first state to a second state when the speed of the vehicle engine is greater than a speed which represents a stalled condition and, conversely, switches from the second state to the first state when the speed of the vehicle engine is below the minimum idle speed and at a speed which represents a stalled condition.

A gate 22 is connected to the bistable switches 14 and 20 and is responsive to the states thereof for energizing the vehicle engine starter motor 24 when the speed of the vehicle engine is at a speed which represents a stalled condition and the speed of the vehicle is above the predetermined minimum speed. The vehicle engine is cranked by the starter motor 24 so as to maintain the operation of the engine driven accessories. If the vehicle engine should start while the starter motor 24 was cranking the engine, the increase in speed thereof would result in an increase in the output of the tachometer circuit 16 to switch the bistable switch 20 from its first state to its second state at which time the gate 22 would deenergize the starter motor 24. If the vehicle engine does not start and the speed of the vehicle decreases below the predetermined minimum,

the output of the tachometer circuit 12 decreases and the bistable switch 14 switches from its second state to its first state. The gate 22 is responsive thereto for deenergizing the vehicle engine starter motor 24. As the gate 22 will not energize the vehicle engine starter motor 24 while the vehicle speed is below the predetermined minimum speed, it is required that the vehicle engine be initially started in the conventional manner when the vehicle is at rest. Consequently, the requirement of a manual start is not altered by the foregoing described system including the requirement that the transmission selector lever be placed in park or neutral position.

Referring to FIG. 2 there is shown an example of a circuit whichcould be used in the mechanization of the system previously described with reference to FIG. 1. The wheel speed sensor 10 includes a magnetically operated reed switch 26 in series with a current limiting resistor 28 across the vehicle battery 30. The'reed switch 26 is positioned adjacent the face of a disk 32 which is rotated by an input shaft 34 which in turn is rotated by a member of the vehicle drive train such as a vehicle rear wheel. Consequently, the rate of rotation of the disk 32 is directly proportional to the speed of the vehicle. The disk 32 is magnetized so as to have alternating north and south magnetic poles therearound. Upon rotation of the disk 32, the reed switch 26 is alternately opened and closed thereby at a rate directly proportional to the speed of rotation of the input shaft 34 and, consequently, the speed of the vehicle. The

wheel speed sensor supplies an output from between the reed switch 26 and the resistor 28 which is comprised of a series of current pulses supplied by the vehicle battery 30 through the resistor 28 when the reed switch 26 is periodically opened and closed. The output of the wheel speed sensor 10 is supplied to a differentiating capacitor 36 in the tachometer circuit 12. The remaining side of the differentiating capacitor 36 is connected to ground through resistor 38 and to the anode of a diode 40. The cathode of the diode 40 is connected to ground through a filtering circuit including a capacitor 42 and a resistor 44. When the reed switch 26 is opened, a voltage pulse is developed across the resistor 38 while the capacitor 36 is charging, which pulse is coupled to the capacitor 42 and the resistor 44 through the diode 40. When the reed switch 26 is closed, the capacitor 36 discharges through the reed switch 26 and the resistor 38. The diode 40 prevents the capacitor 36 from discharging through the resistor 44 and the capacitor 42. As the reed switch 26 is alternately opened and closed by the rotation of the disk 32, the capacitor 42 is charged by the pulses coupled thereto through the diode 40 to a potential which is directly proportional to the rate of rotation of the disk 32 and, consequently, the speed of the vehicle.

The output of the tachometer circuit 12 is the charge on the capacitor 42 which is coupled to the base electrode of an NPN transistor 46 in the bistable switch 14 through a resistor 48. The collector electrode of the transistor 46 is connected to the positive terminal of the vehicle battery 30 through a resistor 49 and the emitter electrode thereof is connected to ground through a resistor 50. The bistable switch 14 also includes a PNP transistor 52 having its base electrode connected to the collector electrode of the transistor 46 through a resistor 53, its collector electrode connected to ground through a resistor 54 and its emitter electrode connected to the positive terminal of the vehicle battery 30. The bistable switch 14 supplies an output from the collector electrode of the transistor 52, which output is the potential developed across the resistor 54. When the speed of the vehicle is zero, the capacitor 42 in the tachometer circuit 12 is fully discharged. Consequently, the transistors 46 and 52 in the bistable switch 14 are biased into nonconduction. Therefore, the output of the bistable switch 14 at the collector electrode of the transistor 52 is ground potential. As the vehicle speed increases from zero, the capacitor 42 is charged to a potential directly related to the speed of the vehicle as previously described. The circuit parameters are chosen such that at a predetermined speed, the capacitor 42 is charged to a potential which biases the transistor 46 into conduction which in turn biases the transistor 52 into conduction. The output of the bistable switch 14 then switches from ground to the potential of the vehicle battery 30. Conversely, when the speed of the vehicle decreases below the predetermined minimum speed, the transistors 46 and 52 are biased into nonconduction to again supply ground potential at the output of the speed switch 14.

The tachometer circuit 16 receives an input from the vehicle ignition system 18 which includes a set of contacts 56 in the ignition switch, which are closed when the ignition switch is in an on position, in series with a primary winding 58 of the vehicle ignition coil 59 and the breaker contacts 60, the foregoing series circuit being connected in parallel with the vehicle battery 30. The ignition system 18 also includes a secondary winding 62 of the ignition coil 59 which supplies a high voltage pulse to the vehicle spark plugs through a distributor 64. The ignition system 18 supplies an output to the tachometer circuit 16 from between the primary winding 58 and the breaker contacts 60, which output is a series of pulses having a frequency directly proportional to the speed of the vehicle engine. This series of pulses is supplied to the base electrode of a transistor 66 through a signal conditioning circuit 68 which filters out the high frequency components. The signaling conditioning circuit 68 includes a resistor 70 connected between the output of the ignition system 18 and the anode of a diode 72 whose cathode is connected to ground through a filtering circuit including a capacitor 74 in parallel with the series combination of a resistor 76 and a resistor 78. A resistor 80 is connected between the anode of the diode 72 and ground. The signaling conditioning circuit 68 supplies an output from between the resistors 76 and 78, which output is applied to the base electrode of the transistor 66. The amplitude of the pulse output of the ignition system 18 is reduced by the resistor 70. The pulse developed across the resistor 80 is coupled through the diode 72 to the capacitor 74 and the resistors 76 and 78 which filters out the high frequency components and applies the resulting pulse to the base electrode of the transistor 66.

The emitter electrode of the transistor 66 is connected to ground and the collector electrode thereof is connected to the positive terminal of the vehicle battery 30 through a resistor 82. The pulses coupled to the base electrode of the transistor 66 bias the transistor 66 into conduction for the duration of each individual pulse.

The signal conditioner 68 supplies an output at the collector electrode of the transistor 66 which is comprised of a series of pulses supplied by the vehicle battery 30 through the resistor 82 when the transistor 66 is biased into nonconduction. The output of the signal conditioner 68 is supplied to a differentiating capacitor 84 in the tachometer circuit 16. The remaining side of the differentiating capacitor 84 is connected to ground through a resistor 86 and to the anode of a diode 88. The cathode of the diode 88 is connected to ground through a filtering circuit including a capacitor 90 and a resistor 92. When the transistor 66 is biased into nonconduction, a voltage pulse is developed across the resistor 86 while the capacitor 84 is charging, which pulse is coupled to the capacitor 90 and the resistor 92 through the diode 88. When the transistor 66 is biased into conduction, the capacitor 84 discharges through the transistor 66 and the resistor 86. The diode 88 prevents the capacitor 84 from discharging through the resistor 92 and the capacitor 90. As the transistor 66 is alternately biased into conduction and nonconduction by the opening and closing of the breaker contacts 60 in the ignition system 18, the capacitor 90 is charged by the pulses coupled thereto through the diode 88 to a potential which is directly proportional to the rate of the opening and closing of the breaker contacts 60 and, consequently, the speed of the vehicle engine.

The output of the tachometer circuit 16 is the charge on the capacitor 90 which is coupled to the base electrode of an NPN transistor 94 in the bistable switch 20 through a resistor 96. The collector electrode of the transistor 94 is connected to the positive terminal of the vehicle battery 30 through a resistor 95 and the emitter electrode thereof is connected to ground through a resistor 98. The bistable switch 16 also includes a PNP transistor 100 having its base electrode connected to the collector electrode of the transistor 94 through a resistor 101, its collector electrode connected to ground through a resistor 102 and its emitter electrode connected to the positive terminal of the vehicle battery 30. The bistable switch 20 supplies an I output from the collector electrode of the transistor 100, which output is the potential developed across the resistor 102. When the speed of the vehicle engine is zero, the capacitor 90 in the tachometer circuit 16 is fully discharged. Consequently, the transistors 94 and 100 in the bistable switch 20 are biased into nonconduction. Therefore, the output of the bistable switch20 at the emitter electrode of the transistor 100 is ground potential. As the vehicle engine speed increases from zero, the capacitor 90 is charged to a potential directly related to the speed of the vehicle engine as previously described. The circuit parameters are chosen such that at a predetermined speed, the capacitor 90 is charged to a potential which biases the transistor 94 into conduction which in turn biases the transistor 100 into conduction. The output of the bistable switch 100 then switches from ground to the potential of thevehicle battery 30. Conversely, when the speed of the vehicle engine decreases below the predetermined minimum speed, the transistors 94 and 100 are biased into nonconduction to again supply ground potential at the output of the bistable switch 20.

The gate 22 includes a PNP transistor 106 and an NPN transistor 108, the collector electrode of the transistor 106 being connected to the emitter electrode of the transistor 108 and the emitter electrode of the transistor 106 being connected to the collector electrode of the transistor 108. The collector electrode of the transistor 106 and the emitter electrode of the transistor 108 are connected to ground. The emitter electrode of the transistor 106 and the collector electrode of the transistor 106 are connected to the positive terminal of the vehicle battery 30 through a resistor 110 and are connected to the base electrode of an NPN transistor 1 12. The collector electrode of the transistor 112 is connected to the positive terminal of the vehicle battery-30 and the emitter electrode thereof is connected to ground through a relay coil 114. The relay coil 114 controls a set of normally open relay contacts 116 which are connected in series with a starter motor solenoid 118 across the vehicle battery 30. The output of the bistable switch 14, at the collector electrode of the transistor 52 is connected to the base electrode of the transistor 106 and the output of the bistable switch 20 at the collector electrode of the transistor102 is connected to the base electrode of the transistor 108 through resistor 119. The base electrode of the transistor 108 is connected to ground through a resistor 120. The output of the gate 22 is the potential of the vehicle battery 30 supplied to the starter motor solenoid 1l8through the set of normally open relay contacts 116 when the relay coil 114 is energized.

The starter motor solenoid 118 is connected in series with a park and neutral safety switch 121 which is closed when the vehicle transmission selector lever is in neutral or park position and a set of contacts 122 which are closed when the vehicle ignition switch is in the start position. This series combination is connected across the vehicle battery. 30, the switch 121 and the contacts 122 being in parallel with the set of normally open relay contacts 116; The starter motor solenoid 118 controls a set of normally open relay contacts 124 which are connected in series with the starter motor 24 across the vehicle battery 30. When either the set of normally open relay contacts 116 are closed or the switch 121 and the contacts 122 are closed, the starter motor solenoid 118 is energized to close the set of normally open contacts 124 and connect the vehicle battery 30 across the starter motor 24 which is energized to crank the vehicle engine.

When the speed of the vehicle is below the predetermined minimum speed, the base electrode of the transistor 106 is grounded through the resistor 54 in the bistable switch 14. Consequently, the transistor 106 is biased into conduction to bias the transistor 112 into nonconduction and maintain the relay coil 114 deenergized. Therefore, when the vehicle engine is not running while the vehicle speed is below the predetermined minimum speed, thestarter solenoid 118 can be energized to start the vehicle engine only by positioning the transmission selector lever into park or neutral position to close the contacts 121 and rotating the ignition switch to start position to close the contacts 122.

When the vehicle engine is running, the output of the bistable switch 20 is the battery potential. Consequently, the transistor 108 is biased into conduction to bias the transistor 112 into nonconduction and maintain the relay coil 114 deenergized. From the foregoing it can be seen that the set of normally open relay contacts 116 are maintained open when either the vehicle speed is below the predetermined minimum or the speed of the vehicle engine is above the speed which represents a stalled condition. The transistor 112 is biased into conduction only when both the transistors 106 and 108 are biased into nonconduction, which condition exists only when the vehicle speed is above the predetermined minimum speed and the vehicle engine has stalled. When this condition exists, the relay coil 114 is energized to close the set of normally open relay contacts 116 to energize the starter motor solenoid 118 and connect the battery 30 across the starter motor 24. The starter motor 24 will be energized to crank the vehicle engine so as to maintain operation of the engine driven accessories until the vehicle speed decreases below the predetermined minimum speed or until the vehicle engine restarts.

In the foregoing manner the engine driven accessories are operated during engine stall only during the period when such operation is required.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be. considered as limiting or restricting the invention, since many modifications may be made by the exercise of skill in the art without dewhen the vehicle engine stalls while the vehicle is in motion and the normal start circuit is disabled, the motor vehicle including a starter motor for cranking the vehicle engine, comprising engine speed tachometer means responsive to the speed of the engine for generating an output signal related to the engine speed;

'vehicle speed tachometer means responsive to the speed of the vehicle for generating an output signal related to the vehicle speed; and circuit means independent of the normal start circuit connected to the engine speed tachometer means, the vehicle speed tachometer means and the starter motor and responsive to the out- 

1. An apparatus for automatically maintaining the operation of motor vehicle engine driven accessories when the vehicle engine stalls while the vehicle is in motion and the normal start circuit is disabled, the motor vehicle including a starter motor for cranking the vehicle engine, comprising engine speed tachometer means responsive to the speed of the engine for generating an output signal related to the engine speed; vehicle speed tachometer means responsive to the speed of the vehicle for generating an output signal related to the vehicle speed; and circuit means independent of the normal start circuit connected to the engine speed tachometer means, the vehicle speed tachometer means and the starter motor and responsive to the output signals of the engine speed tachometer means and the vehicle speed tachometer means for energizing the starter motor without operator action when the output of the engine speed tachometer means represents an engine speed less than the minimum idle speed of said engine and the output of the vehicle speed tachometer means represents a vehicle speed above a predetermined minimum speed, said energizing circuit being maintained until the engine exceeds the minimum idle speed so as momentarily to provide accessory operation even though the engine does not start. 